1. Field of the Invention
The present invention relates to a hydraulic pump assembly for use in combination with an accumulator for supplying hydraulic fluid under pressure to the accumulator through an inlet check valve associated thereto.
2. Discussion of the Background
In the case that the accumulator is in the form of a gas type accumulator adapted to a hydraulic control system, a small amount of gas leaks out through a diaphragm of the accumulator and is mixed with the hydraulic fluid under pressure in the accumulator. When the hydraulic fluid is circulated with the gas into a fluid reservoir through the hydraulic control system, there occur fine air bubbles in the fluid reservoir. Subsequently, the air bubbles are inevitably sucked into the hydraulic pump, resulting in a decrease in pumping efficiency of the pump due to compression thereof. For this reason, a conventional hydraulic pump of small displacement capacity does not produce sufficient hydraulic pressure for the control system.